The development of selective COX-2 inhibitors has reduced the gastrointestinal liability of non-steroidal anti- inflammatory drugs (NSAIDs) while maintaining anti-inflammatory and analgesic activities. Lumiracoxib, a structural analog of diclofenac, is 500-fold more selective for COX-2 than COX-1. Currently, the basis for this selectivity remains unclear. The primary goal of the proposed research is to gain a better understanding of the structural and chemical determinants for the selective inhibition of COX-2 by lumiracoxib. To achieve this goal, lumiracoxib and chemical derivatives of lumiracoxib will be synthesized and several active site- directed mutants of COX-2 will be effectively designed and expressed. The R120A, Y355F, S530A, V349A, V349L and V523I mutants will be screened against lumiracoxib using inhibition kinetics assays and fluorescence quenching methods to determine the binding mode of lumiracoxib in the COX-2 active site. In addition, structural analogs of lumiracoxib will be screened to establish which chemical components on the molecule impart selectivity. To compliment these functional studies, X-ray protein crystallography will be performed on lumiracoxib-bound COX-2 to confirm the binding mode of lumiracoxib in the COX active site. [unreadable] [unreadable]